Preparing method for hydroxyurea

The invention discloses a preparing method for hydroxyurea. The preparing method comprises the steps that methyl carbamate is added into a sodium hydroxide solution, then a hydroxylamine aqueous solution is dripped, and a condensation reaction is carried out after dripping is completed; pH is regulated to range from 7 to 8 through hydrochloric acid after the reaction is completed; then 70-80% of water is distilled off through decompression at the temperature of 58-62 DEG C, and then suction filtration is carried out immediately; filter liquor is added into cationic resin to be decolored and then subjected to suction filtration; filter liquor is cooled to 0-5 DEG C for heat-preservation crystallization, then suction filtration is carried out, a filter cake is washed twice through 0-5 DEG C cold water and then dried, and the hydroxyurea product is obtained. The method is easy to implement and practical, treatment steps are shortened, the yield of the hydroxyurea product is increased, solid waste and waste liquid are reduced, pollution to the environment is reduced, and environment friendliness is achieved.